Gold futures are up 2% at just after 8.30 a.m. GMT (4.30 a.m. ET):
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Silver is even higher, over 3%:
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Market watchers are pinning the spikes on the weak dollar, which dipped last night after the Fed hiked rates.

Mike van Dulken, head of research at Accendo Markets, says in an email on Thursday morning: "Gold has been a clear winner from the US dollar's sharp sell off following the Fed's rate hike, as the precious metal halts its downtrend to post fresh two-week highs.

"In an unusual bullish move for the non-yielding safe haven asset after a rate hike, this can be entirely attributed to the aforementioned USD weakness, as Wilders' Dutch election defeat eases some fears of a populist European backlash."

Ken Odeluga, a market analyst at City Index, told BI: "The key for the moment seems to be more about gold's role as a counterweight to the dollar and, more precisely, as the inverse of the Federal Reserve's willingness to create more ideal dollar conditions by tightening policy."

While Wednesday's rate hike from the Fed was priced in, Odeluga says: "The lack of clear signals about plans to narrow monetary accommodation further —none in the statement and none discernible in chair Janet Yellen's press conference—meant that some of the dollar strength actually had to be unwound. The speed of at which that unwind happened seems to have attracted the attention of speculative gold bugs."

He adds that he doesn't think the price bump is sustainable, saying: "We don't see the move as sustainable, unless markets are delivered of a proper cross-asset shock in the near term. Perhaps a surprise victory by Marine Le Pen in French elections would qualify, though the probability of that happening has been reduced somewhat by the election result in the Netherlands."